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Choosing a storage platform: P2

What application or applications will be supported on this storage platform?

Understanding requirements of the application or applications placed in service on the storage platform is a critical piece of information needed when choosing a storage platform. Probably the best way to illustrate this issue is to look at a storage platform like EMC’s Isilon platform. It scales extremely well when presenting NAS volumes to hundreds or even thousands of clients. Performance increases almost linearly with each added shelf because the I/O is distributed across all of the nodes (shelves) in the cluster. The size of existing volumes can be expanded or reduced without taking volumes offline and shelves can be added or removed from production clusters without service interruption; this allows for tremendous flexibility in adapting to rapidly changing storage needs. However, if you intend to run a large OTP database, Isilon is probably the wrong storage platform for the job. The Isilon platform provides reasonably good throughput to each client and can sustain that throughput to a large number of clients simultaneously, but it is not a great choice when very high performance is needed for only a couple of clients (something typical of OTP databases). Additionally, most OTP databases are going to perform best when a LUN is presented via a SAN infrastructure but Isilon performs best when presenting NAS filesystems.

Do multiple applications intended for use on this storage platform have significantly different requirements? Some storage platforms perform well in a SAN configuration but poorly in a NAS configuration, others perform well in a NAS configuration but poorly in a SAN configuration.Some perform well in one configuration or the other but not both simultaneously, and some storage platforms do a reasonably good job when simultaneously publishing both SAN and NAS volumes. Knowing how you intend to use your storage can help narrow the choices considerably.

What are the performance requirements needed for your applications?

One important, but often overlooked, aspect when evaluating performance needs of a storage platform is the labor costs incurred by a slow system. When end users incur delays that inhibit their ability to complete their work quickly, labor costs increase. Understanding how storage performance impacts the interactive performance of the application utilizing that storage is critical to evaluating your performance needs. For example, if a $50,000 investment is needed to double the interactive performance of an POS application and the current response time is .1 seconds and the increased performance results in a new response time of .05 seconds, the investment in the higher performing system was probably a waste of money. However, if the current response time is 30 seconds and a faster storage system will reduce it to 15 seconds then the investment may be warranted. If this system supports a call center staffed with 100 employees taking orders and if the average order is $20 and the time savings due to the increased interactive performance allows for 4 additional calls per day / per employee. The daily ROI would be $8000 dollars per day with the initial investment paid for in only 7 days! Even if the cost for a faster storage platform in this example had been $500,000 it would have still been a very smart investment.

What are the recurring costs for administering the storage?

Do I already have staff trained to administer this storage platform and what will it cost to keep my staff current as software is updated? Continued training across multiple storage platforms can be costly and a lack of training can be even more costly if it leads to a critical mistake.

What are the recurring costs for H/W and S/W maintenance and (very important) will these costs change significantly in the 2nd year, 3rd year, 4th year, etc…?

Finally, it is important to remember that many considerations we make when choosing a storage platform are interdependent. For example, a comprehensive report detailing the expected ROI for different storage platforms may open the “purse strings” when it comes to budgeting. A need for extremely High Availability and Disaster recovery may lead to compromises on performance, the applications we use may have better support on certain vendor’s storage platforms (especially related to backups and cloning), etc… It is critically important to consider all aspects of your computing environment before choosing a storage platform.